How to get UPC from Item ID ?

Is there a way to get the UPC of an active listing from its Item ID (also called Item number) ? I have tried out various calls like findItemsByProduct in the Finding API, findItemsAdvanced, findItemsByKeywords, GetSingleItem, GetMultipleItems, but have had no success with any of them. The ItemSpecifics container in the response returns everything except the UPC. Neither is it seen in the container.

Is Ebay deliberately blocking requests for UPC ? if not, I request anyone knowledgeable about this to suggest me a suitable solution for this problem.

Thanks for your reply. I checked out the Finding API but couldn't spot it. Could you please tell me which call in the finding API it is or even better, if you could give me the URL for the Finding API call that returns the productID when searched by itemID ?

My aim is to find the UPC from the item ID also known as eBay item number which, for example, for this Michael Kors Carryall Shoulder Bag is: 182811086957 . Its UPC is : 191262027277 which is what the call should return in response.